With the advance of science and technologies, various types of advertising signboards are developed, and an LED advertising signboard is one of the most popular advertising signboards. In general, advertising signboards are mounted on elevated and noticeable areas or people crowded areas, and thus the advertising signboards are often mounted on the glass curtain walls of high-rise buildings. However, since an LED advertising signboard is generally composed of a plurality of LED units through which very few light is allowed to pass, the LED advertising signboard will block the ambient light passing through a glass curtain wall of a building when being mounted on the glass curtain wall, so that the light cannot enter the building from outdoors.